Desulfurization absorption tower

ABSTRACT

A desulfurization absorption tower, a method for setting up the same and a method for operating the same. The tower may include an internal anti-corrosion layer that may be used for contacting the flue gas and the desulfurization absorption liquid, may define the tower chamber, and may include stainless steel plate whose thickness is 1.0 mm to 6.0 mm. The tower body may include an external supporting layer that may be used for supporting the anti-corrosion layer and may include carbon steel. The supporting layer and the anti-corrosion layer may be designed to jointly bear a load, wherein the supporting layer may be designed to bear a large part of the load, and the anti-corrosion layer may be designed to bear a small part of the load.

This application is a divisional of U.S. application Ser. No.15/828,547, filed on Dec. 1, 2017, which claims priority under 35 U.S.C.§ 119 of Chinese Patent Application No. 201710533738.8, filed on Jul. 3,2017, both of which are hereby incorporated herein in their entireties.

TECHNICAL FIELD

The disclosure relates to a desulfurization absorption tower, especiallyan ammonia-process desulfurization absorption tower, having ananti-corrosion structure. The disclosure relates to a setup method andan operating method of such a desulfurization absorption tower.

BACKGROUND

A desulfurization absorption tower, for example, an ammonia-processdesulfurization absorption tower, is a reaction still for acid-baseneutralization reactions. In the desulfurization absorption tower, fluegas containing acid substances, such as SO₂ and HCl, and alkalinesubstances, such as those in absorption liquid, flow in oppositedirections, and acid-base neutralization reactions occur, and producesalts, when the flue gas and the alkaline substances contact each other.When the concentration of the resulting salt solution in the towerchamber rises sufficiently, crystal particles may be precipitated fromthe salt solution. The acid substances, the alkaline substances, thesalt solution and the crystal particles may corrode and abrade the towerbody.

Glass flakes or rubbers are widely used in the desulfurizationabsorption tower as an anti-corrosion lining of the tower. Because theenvironment in the tower chamber is corrosive during operation of thedesulfurization absorption tower, the desulfurization absorption towerlined with glass flakes or rubbers has a short continuous operatingcycle and a short service life. According to long-term use experienceworldwide, the service life of the tower body ranges from 5 years to 10years, the anti-corrosion lining needs to be replaced once every 3 to 5years, and the daily maintenance workload is large. In addition, rawmaterials and adjuvants of such a desulfurization absorption tower areflammable, volatile and toxic. Therefore, the construction environmentis bad, and there is a risk of fire during construction.

A patent document CN201288543Y discloses a desulfurization absorptiontower with a reinforced concrete structure, of which the tower bodyincludes an internal anti-corrosion lining and an external reinforcedconcrete layer connected to the anti-corrosion lining. Theanti-corrosion lining is an anti-corrosion plate made of a polymermaterial, and the anti-corrosion plate is cast together with thereinforced concrete layer and is fixed through an anchor cast in thereinforced concrete layer. In such a desulfurization absorption tower,the anti-corrosion lining is prone to damage, and it is difficult totimely find the damage to the anti-corrosion lining. As thedesulfurization absorption liquid may enter into the reinforced concreteto corrode the reinforced concrete after the anti-corrosion lining isdamaged, the tower body is prone to damage. Such a desulfurizationabsorption tower has a short continuous operating cycle and a shortservice life, the materials are flammable and toxic, and repair isdifficult when the desulfurization absorption tower is damaged. A patentdocument CN201208545Y also discloses a similar desulfurizationabsorption tower, and the technical features thereof are similar.

A patent document CN203090733U discloses a desulfurization absorptiontower, which includes a tower body made of glass fiber reinforcedplastics. A wear-resistant layer is disposed on an inner surface at thebottom of the tower body, to enhance the wear-resistant property of theinner surface at the bottom. It is difficult to ensure the strength ofsuch a desulfurization absorption tower, and less flue gas is treatedthan other towers of equal size. When the amount of flue gas to betreated is over 500,000 Nm³/h, the diameter of the desulfurizationabsorption tower made of glass fiber reinforced plastics is more than 9m, but a tower of glass fiber reinforced plastics with a large towerdiameter has a risk of overall collapse.

A patent document CN201959715U discloses a desulfurization absorptiontower made of stainless steel and used for treating sintering machineflue gas, wherein the whole tower body is made of a stainless steelmaterial. Such a desulfurization absorption tower has defects such as ahigh investment cost, a great construction difficulty, and difficulty inmeeting requirements of different working conditions.

A patent document CN204816188U also discloses a desulfurizationabsorption tower, of which the tower body is formed by stainless steelplates welded together. Such a desulfurization absorption tower also hasa high investment cost, a great construction difficulty, and difficultyin meeting requirements of different working conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is explained exemplarily in detail below by meansof embodiments and with reference to the accompanying drawings. Theembodiments do not limit the present invention, but are used to betterunderstand the present invention. Schematic accompanying drawings aredescribed briefly as follows:

FIG. 1 is a schematic front view of an embodiment of a desulfurizationabsorption tower in accordance with the principles of the invention;

FIG. 2 is a schematic top view of an embodiment of a desulfurizationabsorption tower in accordance with the principles of the invention,wherein a supporting layer is constructed as a supporting frame; and

FIG. 3 is a schematic front view of an embodiment of a desulfurizationabsorption tower in accordance with the principles of the invention,wherein a supporting layer is constructed as an outer cylinder.

DETAILED DESCRIPTION

Apparatus and methods for flue-gas desulfurization are provided. Theapparatus may include, and the methods may involve, an anti-corrosionlayer. The anti-corrosion layer may include stainless steel plate. Thestainless steel plate may include steel that has been cast, rolled,extruded, or otherwise fabricated. The stainless steel plate may includesheet metal, plate metal, or metal in any other suitable form. Thestainless steel plate may be monolithic or may include one or morestainless steel plate elements. The elements may be joined by welds,mechanical fasteners, such as bolts, or by any other suitable method.The elements may be braced to a frame. The elements may be braced to oneor more other stainless steel elements.

The stainless steel plate may be configured to contact the flue gas. Thestainless steel plate may be configured to contact a desulfurizationabsorption liquid, the plate having a mass that has a gravitationalload.

The apparatus may include a supporting layer. The supporting layer mayinclude a carbon steel support. The carbon steel support may beconfigured to support the plate. The stainless steel plate and thecarbon steel support jointly support the load.

The carbon steel support may bear more of the load than does the steelplate.

The stainless steel plate may have a thickness in the range 1.0 mm to6.0 mm.

The plate thickness may be about 1 mm.

The plate thickness may be about 1.5 mm.

The plate thickness may be about 2.0 mm.

The plate thickness may be about 2.5 mm.

The plate thickness may be about 3.0 mm.

The plate thickness may be about 3.5 mm.

The plate thickness may be about 4.0 mm.

The plate thickness may be about 4.5 mm.

The plate thickness may be about 5.0 mm.

The plate thickness may be about 5.5 mm.

The plate thickness may be about 6.0 mm.

Table 1 shows illustrative plate thickness ranges.

TABLE 1 Illustrative plate thicknesses and ranges. Thickness, limitsinclusive, mm (lower limit only where no upper limit is given)Illustrative Approximate Thickness Lower Upper 1 0.6 1.5 1.5 1 2 2 1.52.5 2.5 2 3 3 2.5 3.5 3.5 3 4 4 3.5 4.5 4.5 4 5 5 4.5 5.5 5.5 5 6 6 5.5—

The steel plate may include a plurality of steel plates. The steelplates may be arranged as an interior layer of a tower.

The steel plate may be included in the interior layer of a tower. Thetower may be configured to apply to the flue gas: a firstdesulfurization absorption liquid having, after application to the fluegas, a first chloride ion concentration; and a second desulfurizationabsorption liquid having, after application to the flue gas, a secondchloride ion concentration that is different from the first chloride ionconcentration.

The steel plate may include: a first composition; and a secondcomposition. The steel plate may define a flue gas guide path. The guidepath may be arranged such that the steel plate contacts the first liquidwith the first composition; and the second liquid with the secondcomposition.

One of the first and second compositions may be used in connection witha liquid having a chloride ion concentration that is less than 10,000mg/L. The other of the first and second compositions may be used with aliquid having a chloride ion concentration that is in the range 10,000to 20,000 mg/L.

The composition that corresponds to the chloride ion concentration thatis less than 10,000 mg/L may be 316L stainless steel.

The composition that corresponds to a chloride ion concentration that isin the range 10,000 to 20,000 mg/L may be 2205 stainless steel or 2605Nstainless steel.

One of the first and second compositions may be used in connection witha liquid that has a chloride ion concentration that is less than 10000mg/L. The other of the first and second compositions may be used inconnection with a liquid that has a chloride ion concentration that isno less than 20,000 mg/L.

The composition that corresponds to the chloride ion concentration thatis less than 10,000 mg/L may be 316L stainless steel.

The composition that corresponds to the chloride ion concentration thatis no less than 20,000 mg/L may be 2507 stainless steel.

One of the first and second compositions may be used in connection witha liquid that has a chloride ion concentration that is in the range10,000 to 20,000 mg/L. The other of the first and second compositionsmay be used in connection with a liquid that has a chloride ionconcentration that is no less than 20,000 mg/L.

The composition that corresponds to the chloride ion concentration thatis in the range 10,000 to 20,000 mg/L may be 2205 stainless steel or2605N stainless steel.

The composition that corresponds to the chloride ion concentration thatis no less than 20,000 mg/L may be 2507 stainless steel.

The steel plate may include a first section including 316L stainlesssteel. The steel plate may include a second section including 2205stainless steel or 2605N stainless steel. The steel plate may include athird section including 2507 stainless steel.

The plate may define a flue gas guide path along which: the firstsection is configured to channel desulfurization absorption liquidhaving a chloride ion concentration that is less than 10,000 mg/L; thesecond section is configured to channel desulfurization absorptionliquid having a chloride ion concentration that is in the range 10,000to 20,000 mg/L; and the third section is configured to channeldesulfurization absorption liquid having a chloride ion concentrationthat is no less than 20,000 mg/L.

The support may have an annular cross-section. The plate may be disposedinterior the cross-section.

The support may include a cylinder. The plate may be disposed interiorthe cylinder.

The support and the plate may be similar in shape; and one of thesupport and the plate may be surrounded by the other of the support andthe plate. For example, the support in part or whole may have ahorizontal cross-section, and the plate in part or whole may have ahorizontal cross-section of the same shape. The shape may be a circle, apolygon (e.g., having 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34,35, 36 or more vertices) or any other suitable shape.

For example, the support in part or whole may have a verticalcross-section, and the plate in part or whole may have a verticalcross-section of the same shape. The shape may be a triangle, a polygon(e.g., having 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36or more vertices) or any other suitable shape.

The support may have a thickness of about 2 mm to about 20 mm.

The support may have a thickness of about 2 mm.

The support may have a thickness of about 4 mm.

The support may have a thickness of 6 mm.

The support may have a thickness of about 9 mm.

The support may have a thickness of about 12 mm.

The support may have a thickness of about 15 mm.

The support may have a thickness of about 20 mm.

Table 2 shows illustrative support thickness ranges.

TABLE 2 Illustrative support thicknesses and ranges. Thickness, limitsinclusive, mm (lower limit only where no upper limit is given)Illustrative Approximate Thickness Lower Upper 2 1.5 2.5 2.5 2 3 3 2.53.5 3.5 3 4 4 3.5 4.5 4.5 4 5 5 4.5 5.5 5.5 5 6 6 5.5 6.5 6.5 6 7 7 6.57.5 7.5 7 8 8 7.5 8.5 8.5 8 9 9 8.5 9.5 9.5 9 10 10 9.5 10.5 10.5 10 1111 10.5 11.5 11.5 11 12 12 11.5 12.5 12.5 12 13 13 12.5 13.5 13.5 13 1414 13.5 14.5 14.5 14 15 15 14.5 15.5 15.5 15 16 16 15.5 16.5 16.5 16 1717 16.5 17.5 17.5 17 18 18 17.5 18.5 18.5 18 19 19 18.5 19.5 19.5 19 2020 19.5 —

The support may include a frame. The frame may circumferentiallysurround the plate.

The frame may include one or more vertical support columns. Two or moreof the support columns may be spaced apart from each other by a spacinginterval of not less than 0.5 m. The spacing may be a horizontalspacing.

A first of the columns may be connected to a second of the columns by awelded joint.

A first of the columns may be connected to a second of the columns by abolt.

One or more of the support columns may have an H-shaped cross section.

The spacing interval may be in the range 1 m to 2 m.

Two or more beams may connect a first of the support columns to a secondof the support columns. The first and second columns may be adjacentcolumns. A first of the beams may be at a first elevation. A second ofthe beams may be at a second elevation. The first elevation may begreater than the second elevation.

The plate may have a first height. The plate may include a plurality ofsteel plates connected together to form an interior layer of a tower.The frame may have a second height. The second height may be 95% to 105%the first height.

The stainless steel plate may include a cylinder that forms an uprightlayer defining an interior of a flue gas desulfurization tower. Theplate may include a bottom face. The bottom face may include a bottomsurface of the interior. The plate may include a top face that forms atop surface of the interior. The top surface may include a shoulderadjacent a passageway that leads out of the tower.

The apparatus may include one or more conduits. One or more, or all, ofthe conduits may traverse the plate. One or more, or all, of theconduits may traverse the support structure. One or more, or all, of theconduits may traverse the plate and the support structure.

One or more of the conduits may include a flue gas inlet configured toguide flue gas into a space defined by the stainless steel plate. One ormore of the conduits may include a flue gas outlet configured to guidecleaned flue gas out of the space. One or more of the conduits mayinclude a desulfurization absorption liquid inlet configured to guidedesulfurization absorption liquid into the space. One or more of theconduits may include a desulfurization absorption liquid outletconfigured to guide used desulfurization absorption liquid out of thespace. One or more of the conduits may include a process water inletconfigured to guide process water into the space.

Methods for constructing a desulfurization reactor for cleaning a fluegas are provided. The methods may include selecting, based on a pressureof the flue gas, a sulfur dioxide concentration of the flue gas, and achloride ion concentration of the flue gas, two or more stainless steelgrades. The methods may include assembling on a desulfurization towerbase a first reactor section that includes a first of the stainlesssteel grades. The methods may include placing contiguous with the firstreactor section a second reactor section that includes a second of thestainless steel grades.

The methods may include:

assembling a carbon steel support outside the reactor; and

fixing the first and second reactor sections to the carbon steelsupport.

Methods for cleaning flue gas are provided. The methods may includeintroducing flue gas into an interior region defined by a stainlesssteel plate interior layer of a desulfurization absorption tower. Themethods may include:

flowing the flue gas up through the tower;

receiving in the interior, through the interior layer, a desulfurizationabsorption liquid;

transferring chloride ion from the flue gas to the desulfurizationabsorption liquid;

contacting the chloride ion with the interior layer; and

guiding the chloride ion out of the interior layer, in a desulfurizationabsorption liquid with a predetermined content of ammonium sulfate, toan ammonium sulfate after-treatment system.

The contacting may include a first contacting of the absorption liquidwith the interior layer at a first location, where steel plate includessteel of a first grade; and, then, a second contacting of absorptionliquid with the interior layer at a second location, where the steelplate includes steel of a second grade. The absorption liquid in thefirst location may have a first chloride ion concentration. Theabsorption liquid in the second location may have a second chloride ionconcentration. The first grade may be preselected for the firstconcentration. The second grade may be preselected for the secondconcentration.

The apparatus and methods may operate stably in a long-term continuousoperation, have a longer service life, and have a relatively lowinvestment cost and a relatively short construction cycle.

The methods may be efficient, and may remove part of the nitrogen oxidesin the flue gas. Absorption liquid, such as an ammonia solution oraqueous ammonia, may be provided or supplemented, for example, in acirculation pipeline or an oxidation tank.

By selecting an appropriate stainless steel material, the constructioncost of the desulfurization absorption tower may be minimized withoutcompromising performance.

The supporting layer may be inexpensive and firm, and may require only areduced thickness, and therefore less expensive, anti-corrosion layer,and thus reduce the construction cost of a desulfurization absorptiontower.

The apparatus and methods may stably operate in a long cycle and have alow security risk may be set up relatively rapidly with a low cost.

Using the apparatus or methods, hazardous substances in the flue gas maybe eliminated in an environment-friendly way.

The steps of illustrative methods may be performed in an order otherthan the order shown and/or described herein. Some embodiments may omitsteps shown and/or described in connection with the illustrativemethods. Some embodiments may include steps that are neither shown nordescribed in connection with the illustrative methods. Illustrativemethod steps may be combined. For example, one illustrative method mayinclude steps shown in connection with another illustrative method.

Some embodiments may omit features shown and/or described in connectionwith the illustrative apparatus. Some embodiments may include featuresthat are neither shown nor described in connection with the illustrativeapparatus. Features of illustrative apparatus may be combined. Forexample, one illustrative embodiment may include features shown inconnection with another illustrative embodiment.

Embodiments may involve some or all of the features of the illustrativeapparatus and/or some or all of the steps of the illustrative methods.

The illustrative apparatus and methods will now be described now withreference to the accompanying drawings in the Figures, which form a parthereof. It is to be understood that other embodiments may be utilizedand that structural, functional and procedural modifications may be madewithout departing from the scope and spirit of the present disclosure.

FIG. 1 shows illustrative desulfurization absorption tower 1, whichincludes a tower body and a tower chamber formed inside the tower body.The tower body is provided with lower flue gas inlet 7 and upper fluegas outlet 10 for guiding flue gas, upper circulating liquid inlet 6 andlower circulating liquid outlet 8 for guiding desulfurization absorptionliquid, and process water inlet 9 for supplementing process water.

Tower 1 is constructed as a basically cylindrical tower. Flue gas outlet10 (shown in part) is constructed as a slender neck.

The tower body includes an internal anti-corrosion layer. Theanti-corrosion layer is used for contacting the flue gas and thedesulfurization absorption liquid, defines the tower chamber, and ismade of a stainless steel plate whose thickness is 1.0 mm to 6.0 mm. Thetower body includes an external supporting layer that is used forsupporting the anti-corrosion layer and is made of carbon steel. Thesupporting layer and the anti-corrosion layer are designed to jointlybear the load of the anti-corrosion layer. The supporting layer isdesigned to bear a large part of the load, for example 70% or more, andthe anti-corrosion layer is designed to bear a small part of the load,for example, 30% or less.

Table 3 shows illustrative values of load distribution between thesupporting layer and the anti-corrosion layer.

TABLE 3 Illustrative values of load distribution between the supportinglayer and the anti-corrosion layer. Illustrative load distribution, % oftotal Supporting layer (minimum) Anti-corrosion layer (maximum) 70 30 7525 80 20 85 15 90 10 95 5 99 1

The desulfurization absorption tower may be a direct exhaust-typestraight desulfurization absorption tower with a chimney, which, forexample, has a height of 60 to 120 m, especially 70 to 100 m, forexample, a height of 80 m or 90 m; or may be a side exhaust-typedesulfurization absorption tower without a chimney, which, for example,has a height of 20 to 80 m, especially 30 to 50 m, for example, a heightof 40 m or 60 m.

The diameter of the desulfurization absorption tower may be 1 m orseveral meters, and may be below 30 m, for example, 5 m, 10 m, 15 m, 20m or 25 m. The diameter and the height of the desulfurization absorptiontower may be selected according to parameters of flue gas to be treated.

The anti-corrosion layer includes bottom plate 2, cylinder 4 and topplate 3. The anti-corrosion layer, for example, may be composed ofstainless steel plate whose thickness is 2 mm. Cylinder 4 may be made upof multiple stainless steel plates. Bottom plate 2 may include stainlesssteel plate that is monolithic with, attached to, or separated apartfrom cylinder 4. Top plate 3 may be include stainless steel plate thatis monolithic with, attached to, or separated apart from cylinder 4. Thestainless steel plates may be connected to each other in a sealing way,and particularly, may be welded together.

In FIG. 1, the supporting layer is made up of supporting columns 5.Columns 5 may be evenly distributed around the anti-corrosion layeralong a circumferential direction. The supporting columns 5 may form asupporting frame. The anti-corrosion layer formed by stainless steelplates welded together is fixed and supported in the supporting frame,and may be, in whole or in part, supported on the supporting columns 5.

FIG. 2 shows illustratively 24 supporting columns 5 that are evenlydistributed along a circumferential direction around cylinder 4 of ananti-corrosion layer. In the circumferential direction of thedesulfurization absorption tower, the supporting columns 5 are connectedto each other, especially welded and/or connected by bolts. Multiplebeams may be disposed at different heights between adjacent supportingcolumns, and the beams may connect the adjacent supporting columns toeach other. The beams may be horizontally arranged. The beams may tiltrelative to the supporting columns, for example, at an angle of 15° to75° with respect to the supporting columns. The beams and the supportingcolumns may be welded and/or connected to each other by bolts.

The height of the supporting column 5 may be about the same as theheight of the anti-corrosion layer. The difference in heights of thesupporting column and the anti-corrosion layer may be ±10 m. Thedifference in heights of the supporting column and the anti-corrosionlayer may be ±5 m. The difference in heights of the supporting columnand the anti-corrosion layer may be ±1 m.

The height of the supporting column may be 95-105% the height of theanti-corrosion layer.

FIG. 3 shows illustratively that the supporting layer is formed by anouter cylinder. The outer cylinder is in a shape the same as that of theanti-corrosion layer, for fixing and supporting the anti-corrosionlayer. For the sake of clarity, some components of tower 1 that areshown in FIG. 1 are not shown in FIG. 3.

The supporting layer may include an outer cylinder and supportingcolumns. In contrast to FIG. 1, the supporting columns may support theouter cylinder. The outer cylinder may support the anti-corrosion layer.The columns may thus indirectly support the anti-corrosion layer.

As mentioned above, the anti-corrosion layer is supported by thesupporting layer. As a supplement, the anti-corrosion layer may also bemechanically connected to the supporting layer, and thus they are fixedtogether. For example, the anti-corrosion layer may be welded togetherwith the supporting layer.

The anti-corrosion layer may include sections that have different typeof support with respect to the supporting layer. For example, one ormore sections of the anti-corrosion layer may be a section that isdirectly supported by the supporting layer. One or more sections of theanti-corrosion layer may be a section that is indirectly supported bythe supporting layer. One or more sections of the anti-corrosion layermay be a section that is not supported by the supporting layer. One ormore sections of the anti-corrosion layer may be a section that is notsupported by the supporting layer.

Direct support may include mechanical fastening. One or more of thesections of the anti-corrosion layer may be fastened to the supportinglayer by one or both of welding and fasteners. Direct support mayinclude load bearing or stabilization by contact between the supportinglayer and the anti-corrosion layer. For example, the supporting layermay include one or both of columns and beams, or any other suitablestructure.

Indirect support may include support of a section by a different sectionthat is supported by the supporting layer.

Cylinder 4 may include two or more sections along a height direction,and stainless steel materials of the sections may be selected accordingto an expected chloride ion concentration of the desulfurizationabsorption liquid during operation of the desulfurization absorptiontower. The chloride ion concentration may be approximately calculatedaccording to parameters of flue gas by means of mathematical modeling.In addition, the chloride ion concentration may also be approximatelyestimated by using data collected during operation of an existingdesulfurization absorption tower. For example, existing data of theexisting desulfurization absorption tower of a similar size for treatingsimilar flue gas can be used.

Table 4 shows illustrative parameters for which 316L stainless steel maybe selected.

TABLE 4 Illustrative parameters for which 316L stainless steel may beselected. Desulfurization Parameter Value Flow rate of raw flue gas48,000 Nm³/h SO₂ concentration in raw flue gas 4,200 mg/Nm³ HClconcentration in raw flue gas 5.3 mg/Nm³ Total dust* concentration inraw flue gas 28.4 mg/Nm³ SO₂ concentration in purified flue gas 21.4mg/Nm³ Total dust concentration (containing 2.6 mg/Nm³ aerosol) inpurified flue gas Amount of escaping ammonia 1.3 mg/Nm³ Recovery rate ofammonia 99.43% *Dust may include particulate matter that is not removedby a particulate matter control unit (such as an electrostatic particleprecipitator or baghouse).

Chloride ion concentrations of desulfurization absorption liquid thatmay be present in connection with a process having desulfurizationparameters such as those of Table 4 may be mainly in two ranges:

-   -   (a) 13,000 to 18,000 mg/L; and    -   (b) 4,000 to 8,000 mg/L.

For example, a stainless steel plate with a material type of 2205 may beused for a section of cylinder 4 that is expected to contact thedesulfurization liquid having a chloride ion concentration of 13,000 to18,000 mg/L. A stainless steel plate with a material type of 316L may beused for a section of cylinder 4 that is expected to contact thedesulfurization liquid having a chloride ion concentration of 4,000 to8,000 mg/L.

Supporting columns 5 may be implemented as H-steel or steel of any othersuitable cross-section. The H-steel may have a width that is, forexample, 250 mm. H-steel members may be placed at intervals (betweenadjacent supporting columns 5) of, for example, 1.9 m.

Methods for implementing a desulfurization absorption tower areprovided. The methods may include:

collecting parameters of flue gas expected to be treated, for example,the amount of the flue gas, pressure of the flue gas, a temperature ofthe flue gas, a sulfur dioxide concentration of the flue gas, a chlorideion concentration of the flue gas, and so on;

designing size, for example, diameter and height, of the desulfurizationabsorption tower according to the parameters of the flue gas;

obtaining a chloride ion concentration of the desulfurization absorptionliquid along a height direction, and determining, according to theobtained chloride ion concentration, sections of the anti-corrosionlayer in the height direction and stainless steel materials of thesections;

designing internal components and pipe orifices of the desulfurizationabsorption tower;

determining a load of the desulfurization absorption tower, and thendetermining a load distribution proportion between the anti-corrosionlayer and the supporting layer, selecting a scheme (an outer cylinder ora supporting frame) of the supporting layer, and calculating thethickness of the anti-corrosion layer; and

constructing a base of the desulfurization absorption tower,constructing the anti-corrosion layer of the desulfurization absorptiontower, and constructing the supporting layer of the desulfurizationabsorption tower, wherein the construction of the anti-corrosion layerand the incremental construction of the supporting layer are carried outalternately.

Methods for operating a desulfurization absorption tower are provided.The methods may include receiving raw flue gas in the tower chamber fromlower flue gas inlet 7 of the desulfurization absorption tower. The fluegas may flow from bottom to top. The flue gas may be cooled, washed anddesulfurized by the desulfurization absorption liquid, which may besprayed via circulating liquid inlet 6. Fine particles may be removedfrom the flue gas. The flue gas may be demisted before arriving at theflue gas outlet 10. Then, purified flue gas that is desulfurized to agreat extent may be discharged from the flue gas outlet 10 at the top ofthe tower. Flue gas outlet 10 may be constructed as a direct exhaustchimney.

The desulfurization absorption liquid may flow back, via circulatingliquid outlet 8, to a corresponding circulation tank and a correspondingoxidation tank. Process water may be continuously supplemented atprocess water inlet 9. Absorption solution may be supplemented tocirculation pipelines and oxidation tanks. Desulfurization absorptionliquid whose ammonium sulfate concentration reaches a predetermineddegree may be conveyed as a slurry to an ammonium sulfateafter-treatment system via circulating liquid outlet 8. The slurry maybe subjected to densification, centrifugal separation, drying andpackaging to produce an ammonium sulfate product. Under somecircumstances, evaporative crystallization may be applied before thedensification procedure.

Table 5, below sets forth illustrative desulfurization processparameters.

TABLE 5 Illustrative parameters for which 316L stainless steel may beselected. Desulfurization Parameter Value Raw flue gas flow rate 510,000Nm³/h SO₂ concentration in raw flue gas 2,200 mg/Nm³ HCl content in theraw flue gas 7.6 mg/Nm³ Total dust concentration in raw flue gas 15.3mg/Nm³, SO₂ concentration in purified flue gas 20.1 mg/Nm³ Total dustconcentration (containing 1.7 mg/Nm³ aerosol) in purified flue gasAmount of escaping ammonia 0.8 mg/Nm³ Recovery rate of ammonia 99.6%,

A desulfurization absorption tower structure appropriate for theparameters set forth in Table 5 may include an internal anti-corrosionlayer and an external supporting layer. The supporting layer may include24 supporting columns 5 that form a steel supporting frame. Theanti-corrosion layer may be formed by a stainless steel plate whosethickness is 4 mm, and may include a bottom plate 2, a top plate 3 and acylinder 4. The anti-corrosion layer may be fixed and supported on theexternal supporting layer. The load may be mainly borne by thesupporting layer. The cylinder 4 may be made up of multiple stainlesssteel plates. Each of the plates may have a thickness of 4 mm and aheight of ⅔ m, and the stainless steel plates may be welded to eachother. The supporting columns may include H steel. The width of the Hsteel may be 350 mm. An interval between adjacent supporting columns maybe 2.5 m.

Because the stainless steel plates in the desulfurization absorptiontower may have a small thickness, compared with the conventional carbonsteel tower having a glass flake lining, the total construction cost ofthe desulfurization absorption tower may be reduced by more than 10%,and the construction timeline may be shortened by about ⅓.

In such a desulfurization absorption tower, the chloride ionconcentration in the desulfurization absorption liquid may beapproximately determined according to the parameters of the flue gas,and the material of the anti-corrosion layer may be selected accordingto an expected chloride ion concentration of the desulfurizationabsorption liquid.

Chloride ion concentrations of desulfurization absorption liquid thatmay be present in connection with a process having desulfurizationparameters such as those of Table 5 may be mainly in two ranges:

-   -   (a) 23000 to 31000 mg/L; and    -   (b) 14000 to 17000 mg/L.

A section of the cylinder 4 may contact desulfurization absorptionliquid having a chloride ion concentration of 23,000 to 31,000 mg/L mayinclude a stainless steel plate of material type of 2507. A section ofthe cylinder 4 expected to contact the desulfurization absorption liquidhaving a chloride ion concentration of 14,000 to 17,000 mg/L may adopt astainless steel plate of material type of 2205. Such a desulfurizationabsorption tower may operate for three years without requiring anoverhaul.

Another desulfurization absorption tower structure appropriate for theparameters set forth in Table 5 may include a tower similar to thedesulfurization absorption tower mentioned previously, but different inthat the thickness of the steel plate of the anti-corrosion layer may be3.5 mm, the supporting layer may be constructed as an outer cylinder,and the outer cylinder may be made of carbon steel whose material typeis Q235 and may have a thickness of 9 mm. Compared with the conventionalcarbon steel tower having a glass flake lining, the total constructioncost may be reduced by approximately 15%, and the construction period ofthe desulfurization absorption tower may be reduced by 1.5 months.

The apparatus may include a desulfurization absorption tower that mayinclude a tower body and a tower chamber that is formed inside the towerbody. The tower body may be provided with a lower flue gas inlet (7) andan upper flue gas outlet (10) for guiding flue gas, an upper circulatingliquid inlet (6) and a lower circulating liquid outlet (8) for guidingdesulfurization absorption liquid, and a process water inlet (9) forsupplementing process water. The tower body may include an internalanti-corrosion layer that is used for contacting the flue gas and thedesulfurization absorption liquid, defines the tower chamber, and may bemade of a stainless steel plate whose thickness is 1.0 mm to 6.0 mm. Thetower body may include an external supporting layer that is used forsupporting the anti-corrosion layer and is made of carbon steel,especially carbon steel whose material type is Q235 or Q345. Thesupporting layer and the anti-corrosion layer may be designed to jointlybear a load, wherein the supporting layer may be designed to bear alarge part of the load, and the anti-corrosion layer may be designed tobear a small part of the load.

The desulfurization absorption tower may be an ammonia-processdesulfurization absorption tower, wherein the process water isproduction make-up water.

The thickness of the stainless steel plate may be 2.0 mm, 2.5 mm, 3.0mm, 3.5 mm, 4.0 mm, 4.5 mm or 5.0 mm.

The anti-corrosion layer may be formed by multiple stainless steelplates connected together.

The anti-corrosion layer may include a bottom plate (2), a cylinder (4),and a top plate (3). The cylinder may be made up of two or more sectionsalong a height direction, and stainless steel materials of the sectionsmay be selected to correspond to an expected chloride ion concentrationof the desulfurization absorption liquid during operation of thedesulfurization absorption tower.

The stainless steel material of the anti-corrosion layer may be selectedfrom stainless steel of the following material types: 316L, 2205, 2605Nand 2507, and the stainless steel material may be selected to correspondto an expected chloride ion concentration of the desulfurizationabsorption liquid during operation of the desulfurization absorptiontower, wherein 316L is selected when the chloride ion concentration ofthe desulfurization absorption liquid is less than 10000 mg/L, 2205 or2605N is selected when the chloride ion concentration of thedesulfurization absorption liquid is 10000 to 20000 mg/L, and 2507 isselected when the chloride ion concentration of the desulfurizationabsorption liquid is 20000 mg/L or more.

The supporting layer may be an outer cylinder and/or a supporting frame.The outer cylinder and the anti-corrosion layer may have the same shape,and may have a thickness of 2 to 20 mm, for example, 4 mm, 6 mm, 9 mm,12 mm or 15 mm.

The supporting frame may be made up of multiple supporting columns (5)that are distributed, possibly evenly distributed, in a circumferentialdirection. The supporting columns may have an interval of not less than0.5 m, an interval of 1 to 2 m, or more. The supporting column may bemade of H-steel.

In the circumferential direction of the desulfurization absorptiontower, the supporting columns (5) may be connected to each other, forexample, by welds and/or bolts. Multiple beams may be disposed atdifferent heights between adjacent supporting columns (5), and the beamsmay connect the adjacent supporting columns to each other. The height ofthe supporting column (5) may be 95-105% of the height of theanti-corrosion layer.

The methods may include setting up the desulfurization absorption tower.The methods may include:

predetermining parameters of flue gas treated during operation of thedesulfurization absorption tower, the parameters including: the amountof the flue gas, pressure of the flue gas, a sulfur dioxideconcentration of the flue gas, and a chloride ion concentration of theflue gas;

obtaining, according to the parameters of the flue gas, an expectedchloride ion concentration of the desulfurization absorption liquidduring operation of the desulfurization absorption tower;

determining, according to the parameters of the flue gas, the size ofthe tower chamber of the desulfurization absorption tower, anddetermining sizes and positions of the flue gas inlet, the flue gasoutlet, the circulating liquid inlet, the circulating liquid outlet, andthe process water inlet;

determining, according to the expected chloride ion concentration of thedesulfurization absorption liquid, sections of the anti-corrosion layerof the desulfurization absorption tower and stainless steel materials ofthe sections;

determining, according to the parameters of the flue gas, a load of thedesulfurization absorption tower, then determining load distributionbetween the anti-corrosion layer and the supporting layer, and thendetermining the thickness of the anti-corrosion layer and the size ofthe supporting layer;

setting up a base of the desulfurization absorption tower according tothe total weight of the desulfurization absorption tower; and

setting up the anti-corrosion layer and the supporting layer on the baseof the desulfurization absorption tower according to determined sizesand materials of the anti-corrosion layer and the supporting layer.

The process of setting up the anti-corrosion layer and the process ofsetting up the supporting layer may be carried out alternately.

The methods may include operating the desulfurization absorption tower.The methods may include:

introducing raw flue gas into the tower chamber of the desulfurizationabsorption tower via the flue gas inlet, wherein the flue gas flows frombottom to top in the tower chamber, and exhausting purified flue gas outof the desulfurization absorption tower via the flue gas outlet;

and spraying the desulfurization absorption liquid from top to bottom inthe tower chamber via the circulating liquid inlet, wherein the flue gasis cooled, washed and desulfurized, and fine particles are removed fromthe flue gas.

Before the flue gas leaves the tower chamber via the flue gas outlet,the flue gas may be demisted.

The methods may include:

supplementing process water via the process water inlet; and

guiding the desulfurization absorption liquid with a predeterminedcontent of ammonium sulfate to an ammonium sulfate after-treatmentsystem via the circulating liquid outlet.

The features disclosed in the present application can be combined witheach other arbitrarily, as long as such combinations are notself-contradictory. All the combinations are contents disclosed in thepresent application.

All ranges and parameters disclosed herein are understood to encompassany and all subranges subsumed therein, and every number between theendpoints. For example, a stated range of “1 to 10” should be consideredto include any and all subranges between (and inclusive of) the minimumvalue of 1 and the maximum value of 10; that is, all subranges beginningwith a minimum value of 1 or more (e.g. 1 to 6.1), and ending with amaximum value of 10 or less (e.g. 2.3 to 9.4, 3 to 8, 4 to 7), andfinally to each number 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 containedwithin the range. All percentages, ratios and proportions herein are byweight unless otherwise specified.

While this invention may be embodied in many different forms, there aredescribed in detail herein specific embodiments of the invention. Thepresent disclosure illustrates principles of the invention, and is notintended to limit the invention to the particular embodimentsillustrated. All patents, patent applications, scientific papers, andany other referenced materials mentioned herein are incorporated byreference in their entireties. The principles of the invention encompassany possible combination of some or all of the various embodimentsmentioned herein, described herein and/or incorporated herein. Theprinciples of the invention encompass any possible combination that alsospecifically excludes any one or some of the various embodimentsmentioned herein, described herein and/or incorporated herein.

Thus, apparatus and methods for flue-gas desulfurization have beenprovided. Persons skilled in the art will appreciate that the presentinvention can be practiced by other than the described embodiments,which are presented for purposes of illustration rather than oflimitation. The present invention is limited only by the claims thatfollow.

What is claimed is:
 1. A method for constructing a desulfurizationreactor for a flue gas to be cleaned, the method comprising: selecting,based on parameters of the flue gas that include an amount of the fluegas, a pressure of the flue gas, a sulfur dioxide concentration of theflue gas, and a chloride ion concentration of the flue gas, two or morestainless steel grades; assembling on a desulfurization tower base afirst reactor section including a first of the stainless steel grades;and placing contiguous with the first reactor section a second reactorsection including a second of the stainless steel grades.
 2. The methodof claim 1 further comprising: assembling a carbon steel support outsidethe reactor; and fixing the first and second reactor sections to thecarbon steel support.
 3. The method of claim 1 wherein the selecting thetwo or more stainless steel grades corresponds to setting anti-corrosionproperties of an interior layer of the reactor contacting the flue gasand defining a flue gas guide path.
 4. The method of claim 1 wherein theselecting includes obtaining, according to the parameters of the fluegas: a first chloride ion concentration of a first desulfurizationabsorption liquid expected during operation of the reactor; and a secondchloride ion concentration of a second desulfurization absorption liquidexpected during operation of the reactor, the second expected chlorideion concentration different from the first expected chloride ionconcentration.
 5. The method of claim 4 wherein the selecting includes:determining according to the first expected chloride ion concentration,the first of the stainless steel grades; and determining according tothe second expected chloride ion concentration, the second of thestainless steel grades.
 6. The method of claim 5 wherein the selectingincludes the first of the stainless steel grades: including 316Lstainless steel corresponding to the first expected chloride ionconcentration being less than 10,000 mg/L; including 2205 stainlesssteel or 2605N stainless steel corresponding to the first expectedchloride ion concentration being in the range 10,000 mg/L to 20,000mg/L; and including 2507 stainless steel corresponding to the firstexpected chloride ion concentration being no less than 20,000 mg/L. 7.The method of claim 5 wherein the selecting includes the second of thestainless steel grades: including 316L stainless steel corresponding tothe second expected chloride ion concentration being less than 10,000mg/L; including 2205 stainless steel or 2605N stainless steelcorresponding to the second t expected chloride ion concentration beingin the range 10,000 mg/L to 20,000 mg/L; and including 2507 stainlesssteel corresponding to the second expected chloride ion concentrationbeing no less than 20,000 mg/L.
 8. The method of claim 1 furthercomprising placing contiguous with the second reactor section a thirdreactor section that includes a third of the stainless steel grades. 9.The method of claim 8 further comprising: assembling a carbon steelsupport outside the reactor, and fixing the first, second and thirdreactor sections to the carbon steel support.
 10. The method of claim 8wherein: the first of the stainless steel grades includes 316L stainlesssteel; the second of the stainless steel grades includes 2205 stainlesssteel or 2605N stainless steel; and the third of the stainless steelgrades includes 2507 stainless steel.
 11. The method of claim 1 furthercomprising: determining, based on the parameters of the flue gas: a sizeof the reactor; and sizes and positions of: a flue gas inlet; a flue gasoutlet; a circulating liquid inlet; a circulating liquid outlet; and aprocess water inlet.
 12. The method of claim 1 wherein; the firstreactor section including the first of the stainless grades comprises aninterior of the reactor including steel plate of the first of thestainless steel grades; and the second reactor section including thesecond of the stainless grades comprises the interior of the reactorincluding steel plate of the second of the stainless steel grades. 13.The method of claim 12 wherein a plurality of plates of the first of thestainless steel grades and of the second of the stainless steel gradesare connected together to form the interior of the reactor.
 14. Themethod of claim 12 wherein: the first reactor section including thefirst of the stainless grades comprises the first reactor section steelincluding steel plate of the first of the stainless steel grades; andthe second reactor section including the second of the stainless gradescomprises the second reactor section steel including steel plate of thesecond of the stainless steel grades.
 15. The method of claim 14wherein: an interior of the first reactor section comprises a pluralityof steel plates of the first of the stainless steel grades connectedtogether; and an interior of the second reactor section comprises aplurality of steel plates of the second of the stainless steel gradesconnected together.
 16. The method of claim 1 wherein the reactorincludes stainless steel plate of the two or more stainless steelgrades.
 17. The method of claim 16 wherein the stainless steel plate hasa thickness in the range 1.0 mm to 6.0 mm.
 18. The method of claim 17wherein the thickness is about 2.0 mm.
 19. The method of claim 17wherein the thickness is about 3.0 mm.
 20. The method of claim 17wherein the thickness is about 4.0 mm.
 21. The method of claim 17wherein the thickness is about 5.0 mm.
 22. The method of claim 16further comprising: determining, based on the parameters of the fluegas: a load of the reactor; and a load distribution between the reactorand the support.
 23. The method of claim 22 wherein the carbon steelsupport bears more of the load than does the steel plate.
 24. The methodof claim 2 wherein assembling the carbon steel support includes buildinga frame that circumferentially surrounds the plate.
 25. The method ofclaim 24 wherein building the frame includes spacing vertical supportcolumns apart from each other at an interval not less than 0.5 m. 26.The method of claim 25 wherein the interval is in the range 1 m to 2 m.27. The method of claim 25 wherein spacing vertical support columnsincludes connecting a first of the support columns to a second of thesupport columns by a welded joint.
 28. The method of claim 25 whereineach of the support columns has an H-shaped cross section.
 29. Themethod of claim 24 wherein: building the frame includes determining afirst height of the reactor; and setting a second height of the frame at95% to 105% the first height.
 30. The method of claim 2 wherein theassembling on the desulfurization tower base includes determining theexpected total weight of the reactor and the support.